1. Field of the Invention
The present invention relates to a zigzag wavelength division multiplexer, and in particular to a zigzag wavelength division multiplexer reducing the wavelength shift in the center of a frequency band resulting from temperature changes.
2. Description of the Related Art
FIG. 1A is a schematic perspective view showing a conventional zigzag wavelength division multiplexer. The conventional zigzag wavelength division multiplexer (U.S. Pat. No. 5,859,717) includes a housing 1. A support 2, a first collimator 3, a second collimator 4, a third collimator 5, a fourth collimator 6, a fifth collimator 7 and a sixth collimator 8 are disposed in the housing 1. A first wave filter 9, a second wave filter 10, a third wave filter 11 and a fourth wave filter 12 are disposed in the support 2. The first collimator 3 outputs multi-channel collimated light to the first wave filter 9 at an incident angle. Generally speaking, the incident angle is between 5xc2x0 and 9xc2x0. Preferably, the incident angle is 7xc2x0. Specifically, the wavelength of light passing through the wave filter is changed whenever the incident angle is changed by 0.15xc2x0. Furthermore, the higher the incident angle, the higher the polarization dependent loss (PDL).
In the conventional zigzag wavelength division multiplexer (U.S. Pat. No. 5,859,717), spacers 13 are used to fix the collimators, as shown in FIG. 1B. The spacers 13 can only prevent length change of the collimator resulting from thermal expansion and contraction, but not tilt angle between the collimator and the wave filter. Thus, the adhesive 14 causes tilt angle between the collimator and the wave filter resulting from thermal expansion and contraction, and the tilt angle causes wavelength shift in a frequency band and subsequent light loss.
An object of the invention is to provide a zigzag wavelength division multiplexer. The zigzag wavelength division multiplexer comprises an intermediate block, an input end and a plurality of output ends. The input end is disposed on one side of the intermediate block and has a first sleeve and an optical collimator. The first sleeve has a first fixing portion having a hole. The axis of the first sleeve is tilted to the plane of the opening of the first sleeve at a first angle. The optical collimator is disposed in the first sleeve and fixed to the first fixing portion. The output ends are disposed on two sides of the intermediate block. Each of the output ends has a second sleeve, a GRIN lens, a first pad, a glass ferrule, a second pad and a wave filter. The second sleeve has a first portion, a second portion and a second fixing portion having a hole. The axis of the first portion is coaxial to that of the second portion. The axis of the second portion is tilted to the plane of the opening of the second portion at a second angle. The GRIN lens is disposed in the first portion and fixed to the second fixing portion. The first pad is disposed on one end of the GRIN lens. The glass ferrule is disposed on the first pad. The second pad is disposed on the opening of the second portion of the second sleeve and the side of the intermediate block. The wave filter is disposed in the second portion and on the second pad. After multi-channel light enters the intermediate block via the input end, the output ends output corresponding channel light, respectively.
The invention has the following advantages. The invention uses sleeves to fix the optical collimators and the wave filters, thus preventing a tilt angle between the optical collimator and the wave filter. In addition, the invention reduces the wavelength shift in the center of a frequency band resulting from temperature changes. Furthermore, the invention uses the sleeves to fix the optical collimators and the wave filters, thus reducing light loss.
A detailed description is given in the following embodiments with reference to the accompanying drawings.